1. Field of the Invention
The present invention generally relates to a motor's stator unit and, more particularly, to a motor's stator unit that can be coupled with a rotor or an impeller to construct a motor or a cooling fan.
2. Description of the Related Art
Conventionally, a motor or a cooling fan includes a base. A shaft tube is arranged on a center of the base. At least one bearing is installed in the shaft tube, so that a rotor is able to rotatably couple with the bearing. The conventional motor or the cooling fan further includes a stator having a silicon steel plate unit that is press fit around the shaft tube to prevent the stator from disengaging from the shaft tube.
Since the silicon steel plate unit is made of metal material, the silicon steel plate unit may excessively compress the shaft tube when fit around the shaft tube by press fitting. This may cause deformation of the shaft tube. The deformed shaft tube may further compress the bearing and therefore result in damage to or deformation of the bearing. As a result, the service life of the motor or the cooling fan is shortened.
Referring to FIG. 1, a modified fixed bearing structure of a DC fan is disclosed by Taiwan Patent No. 519259. The conventional fixed bearing structure 7 includes a base 71 and a shaft seat 72 arranged on a center of the base 71. The shaft seat 72 has an annular groove 721. The upper part of the shaft seat 72 is separated into an inner annular wall 722 and an outer annular wall 723 by the annular groove 721. A stator unit 73 is press fit around the outer annular wall 723. A retaining ring 74 is installed in the annular groove 721 to support the stator unit 73 and to prevent the disengagement of the stator unit 73.
In the modified fixed bearing structure described above, the structure is of high complexity due to the formation process of the inner and outer annular walls 722, 723 and the installation process of the retaining ring 74, resulting in an inconvenient assembly.
Referring to FIG. 2, Taiwan Patent No. M284196 discloses a conventional cooling fan 8 comprising a fan frame 81, a bearing 82 and a stator 83. A central column 811 is arranged on a center of the fan frame 81. The bearing 82 is received in the central column 811. Threads 812 are arranged on upper and lower parts of an outer circumferential wall of the central column 811. The stator 83 may be fit around the central column 811. The stator 83 includes an upper insulation sleeve 831 screwed to the thread 812 on the upper part of the central column 811, as well as an lower insulation sleeve 832 screwed to the thread 812 on the lower part of the central column 811. This structure provides enhanced coupling between the stator 83 and the central column 811.
Disadvantageously, not only does it require forming the threads 812 on the upper and lower parts of the outer circumferential wall of the central column 811, but it also requires forming another two threads on inner circumferential walls of the upper insulation sleeve 831 and the lower insulation sleeve 832 that can be engaged with the threads 812 of the central column 811. As a result, it is inconvenient to manufacture the cooling fan. In addition, it is also required to screw the upper insulation sleeve 831 and the lower insulation sleeve 832 to the central column 811, leading to an inconvenient assembly.
FIG. 3 shows a spindle motor 9 disclosed by Taiwan Patent No. I258912 entitled “SPINDLE MOTOR AND STATOR STRUCTURE THEREOF”. The spindle motor 9 is comprised of a stator 91 and a rotor 92. The stator 91 includes a seat 911, a magnetic-inducing structure 912 surrounding the seat 911, as well as a buffering structure 913 connected between the seat 911 and the magnetic-inducing structure 912.
In the structure of FIG. 3, the buffering structure 913 is located between the seat 911 and the magnetic-inducing structure 912. However, although the magnetic-inducing structure 912 is connected to the seat 911 via the buffering structure 913, the magnetic-inducing structure 912 is liable to compress the seat 911 via the buffering structure 913 since the magnetic-inducing structure 912 is made of metal material. As a result, the seat 911 can become deformed, shortening the service life of the spindle motor 9.